gklib @20230327: error: 'lnlen' may be used uninitialized in this function

[rmottola (Riccardo)]

I suppose it is not a specific PPC issue, but a fact that GCC is being used instead of clang.

 CMakeFiles/GKlib.dir/itemsets.c.o.d -o CMakeFiles/GKlib.dir/itemsets.c.o -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/itemsets.c
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c: In function 'gk_readfile':
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c:113:24: error: 'lnlen' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   if (*lineptr == NULL || *n == 0) {
       ~~~~~~~~~~~~~~~~~^~~~~~~~~~

[rmottola (Riccardo)]

what is the best way to reduce warnings in the portfile? Maybe this is a false flag-

[jmroot (Joshua Root)]

I'm not sure if it works to add something like -Wno-error without specifying a warning class. You might have to patch the CMakeLists.txt to not add -Werror in the first place. Of course if the variable really can be used uninitialized, that should be reported upstream.

[rmottola (Riccardo)]

I have this error too. Compilation is being done with gcc7

/opt/local/bin/gcc-mp-7 -DGKlib_EXPORTS -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/. -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/test -pipe -Os -DNDEBUG -I/opt/local/include -DLINUX -D_FILE_OFFSET_BITS=64 -std=c99 -fno-strict-aliasing -mtune=native -fPIC -Werror -Wall -pedantic -Wno-unused-function -Wno-unused-but-set-variable -Wno-unused-variable -Wno-unknown-pragmas -Wno-unused-label -DNO_X86=ON -DNDEBUG -DNDEBUG2 -DHAVE_EXECINFO_H -O3 -arch ppc -mmacosx-version-min=10.5 -fPIC -MD -MT CMakeFiles/GKlib.dir/io.c.o -MF CMakeFiles/GKlib.dir/io.c.o.d -o CMakeFiles/GKlib.dir/io.c.o -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c: In function 'gk_readfile':
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_math_gklib/gklib/work/GKlib-8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c:113:24: error: 'lnlen' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   if (*lineptr == NULL || *n == 0) {

I doubt this is a PPC only, but more a compiler issue which spits out a warning. Maybe on intel we usually have a different gcc or clang version.

Should maybe warning=errors should be removed or specific initialization warnings suppressed?

[rmottola (Riccardo)]

Out of curiosity I tried using gcc 4.8 (only other available MP compiler there)

gcc-mp-4.8: error: unrecognized command line option '-arch'

[ryandesign (Ryan Carsten Schmidt)]

Please attach the main.log file.

I am not able to reproduce the problem on macOS 12 building using Xcode clang or MacPorts gcc 13. I can't test gcc 7 because it's too old for this OS.

Replying to rmottola:

io.c: In function 'gk_readfile':
io.c:113:24: error: 'lnlen' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   if (*lineptr == NULL || *n == 0) {
       ~~~~~~~~~~~~~~~~~^~~~~~~~~~

gk_readfile uses lnlen only once, at the end of this chunk:

​https://github.com/KarypisLab/GKlib/blob/8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c#L147-L159

char **gk_readfile(char *fname, size_t *r_nlines)
{
  size_t lnlen, nlines=0;
  char *line=NULL, **lines=NULL;
  FILE *fpin;

  gk_getfilestats(fname, &nlines, NULL, NULL, NULL);
  if (nlines > 0) {
    lines = (char **)gk_malloc(nlines*sizeof(char *), "gk_readfile: lines");

    fpin = gk_fopen(fname, "r", "gk_readfile");
    nlines = 0;
    while (gk_getline(&line, &lnlen, fpin) != -1) {

As we see at the top of the function, at this point line is a NULL pointer and lnlen is uninitialized.

gk_getline in turn does this:

​https://github.com/KarypisLab/GKlib/blob/8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c#L101C1-L113

ssize_t gk_getline(char **lineptr, size_t *n, FILE *stream)
{
#ifdef HAVE_GETLINE
  return getline(lineptr, n, stream);
#else
  size_t i;
  int ch;

  if (feof(stream))
    return -1;  

  /* Initial memory allocation if *lineptr is NULL */
  if (*lineptr == NULL || *n == 0) {

The way I read this, in this call, *lineptr (aka line) is NULL, so the second part of the condition checking if *n (aka lnlen which is uninitialized) is 0 is not evaluated, so I don't think the variable is being used uninitialized. You could still report the problem to the developers; it would be simple to just initialize the variable anyway.

HAVE_GETLINE is true on Mac OS X 10.7 or later, so this problem only affects Mac OS X 10.6 and earlier, which is probably why not more people have reported it.

I tried removing these lines from GKlibSystem.cmake (because I could find no way to override this result on the command line):

check_function_exists(getline HAVE_GETLINE)
if(HAVE_GETLINE)
  set(GKlib_COPTIONS "${GKlib_COPTIONS} -DHAVE_GETLINE")
endif(HAVE_GETLINE)

Even so, I did not see an error or warning about uninitialized variable use on macOS 12 with Xcode clang or MacPorts gcc 13. Maybe this warning was improved in later GCC versions to be more accurate.

The build system sets -Werror only when the compiler is GCC. I submitted a PR to stop doing that:

​https://github.com/KarypisLab/GKlib/pull/36